Obesity is a life-threatening disorder in which there is an increased risk of morbidity and mortality arising from concomitant diseases such as type II diabetes, hypertension, stroke, cancer and gallbladder disease.
Obesity is now a major healthcare issue in the Western World and increasingly in some third world countries. The increase in numbers of obese people is due largely to the increasing preference for high fat content foods but also the decrease in activity in most people's lives. Currently about 30% of the population of the USA is now considered obese.
Whether someone is classified as overweight or obese is generally determined on the basis of their body mass index (BMI) which is calculated by dividing body weight (kg) by height squared (m2). Thus, the units of BMI are kg/m2 and it is possible to calculate the BMI range associated with minimum mortality in each decade of life. BMI is more highly correlated with body fat than any other indicator of height and weight. Overweight is defined as a BMI in the range 25-30 kg/m2, and obesity as a BMI greater than 30 kg/m2 (see table below).
Classification Of Weight By Body Mass Index (BMI)BMICLASSIFICATION<18.5Underweight18.5-24.9Normal25.0-29.9Overweight30.0-34.9Obesity (Class I)35.0-39.9Obesity (Class II)>40 Extreme Obesity (Class III)
As the BMI increases there is an increased risk of death from a variety of causes that are independent of other risk factors. The most common diseases associated with obesity are cardiovascular disease (particularly hypertension), diabetes (obesity aggravates the development of diabetes), gall bladder disease (particularly cancer) and diseases of reproduction. The strength of the link between obesity and specific conditions varies. One of the strongest is the link with type 2 diabetes. Excess body fat underlies 64% of cases of diabetes in men and 77% of cases in women (Seidell, Semin Vasc Med, 5:3-14 (2005)). Research has shown that even a modest reduction in body weight can correspond to a significant reduction in the risk of developing coronary heart disease.
There are problems however with the BMI definition in that it does not take into account the proportion of body mass that is muscle in relation to fat (adipose tissue). To account for this, obesity can also be defined on the basis of body fat content: greater than 25% in males and greater than 30% in females.
Obesity considerably increases the risk of developing cardiovascular diseases as well. Coronary insufficiency, atheromatous disease, and cardiac insufficiency are at the forefront of the cardiovascular complications induced by obesity. It is estimated that if the entire population had an ideal weight, the risk of coronary insufficiency would decrease by 25% and the risk of cardiac insufficiency and of cerebral vascular accidents would decrease by 35%. The incidence of coronary diseases is doubled in subjects less than 50 years of age who are 30% overweight. The diabetes patient faces a 30% reduced lifespan. After age 45, people with diabetes are about three times more likely than people without diabetes to have significant heart disease and up to five times more likely to have a stroke. These findings emphasize the inter-relations between risks factors for diabetes and coronary heart disease and the potential value of an integrated approach to the prevention of these conditions based on the prevention of obesity (Perry, I. J., et al., BMJ 310, 560-564 (1995)).
Diabetes has also been implicated in the development of kidney disease, eye diseases and nervous system problems. Kidney disease, also called nephropathy, occurs when the kidney's “filter mechanism” is damaged and protein leaks into urine in excessive amounts and eventually the kidney fails. Diabetes is also a leading cause of damage to the retina at the back of the eye and increases risk of cataracts and glaucoma. Finally, diabetes is associated with nerve damage, especially in the legs and feet, which interferes with the ability to sense pain and contributes to serious infections. Taken together, diabetes complications are one of the nation's leading causes of death.
The first line of treatment is to offer diet and life style advice to patients such as reducing the fat content of their diet and increasing their physical activity. However, many patients find this difficult and need additional help from drug therapy to maintain results from these efforts.
Most currently marketed products have been unsuccessful as treatments for obesity because of a lack of efficacy or unacceptable side-effect profiles. The most successful drug so far was the indirectly acting 5-hydroxytryptamine (5-HT) agonist d-fenfluramine (Redux™) but reports of cardiac valve defects in up to one third of patients led to its withdrawal by the FDA in 1998.
In addition, two drugs have been launched in the USA and Europe: Orlistat (Xenical™) a drug that prevents absorption of fat by the inhibition of pancreatic lipase, and Sibutramine (Reductil™), a 5-HT/noradrenaline re-uptake inhibitor. However, side effects associated with these products may limit their long-term utility. Treatment with Xenical™ is reported to induce gastrointestinal distress in some patients, while Sibutramine has been associated with raised blood pressure in some patients.
Serotonin (5-HT) neurotransmission plays an important role in numerous physiological processes both in physical and in psychiatric disorders. 5-HT has been implicated in the regulation of feeding behavior. 5-HT is believed to work by inducing a feeling of satiety, such that a subject with enhanced 5-HT stops eating earlier and fewer calories are consumed. It has been shown that a stimulatory action of 5-HT on the 5-HT2C receptor plays an important role in the control of eating and in the anti-obesity effect of d-fenfluramine As the 5-HT2C receptor is expressed in high density in the brain (notably in the limbic structures, extrapyramidal pathways, thalamus and hypothalamus i.e. PVN and DMH, and predominantly in the choroid plexus) and is expressed in low density or is absent in peripheral tissues, a selective 5-HT2C receptor agonist can be a more effective and safe anti-obesity agent. Also, 5-HT2C knockout mice are overweight with cognitive impairment and susceptibility to seizure.
It is believed that the 5-HT2C receptor may play a role in obsessive compulsive disorder, some forms of depression, and epilepsy. Accordingly, agonists can have anti-panic properties, and properties useful for the treatment of sexual dysfunction.
In sum, the 5-HT2C receptor is a receptor target for the treatment of obesity and psychiatric disorders, and it can be seen that there is a need for selective 5-HT2C agonists which safely decrease food intake and body weight.
The salts of the present invention comprise the selective 5-HT2C-receptor agonist (R)-8-chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine (Compound 1), which is useful for, inter alia, weight management, including weight loss and the maintenance of weight loss. Compound 1 is disclosed in PCT patent publication WO2003/086303, which is incorporated herein by reference in its entirety.

Various synthetic routes to (R)-8-chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine, its related salts, enantiomers, crystalline forms, and intermediates, have been reported in WO 2005/019179, WO 2006/069363, WO 2007/120517, WO 2008/070111, WO 2009/111004, and WO 2010/148207 each of which is incorporated herein by reference in its entirety.
Combinations of (R)-8-Chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine with other agents, including without limitation, phentermine, and uses of such combinations in therapy are described in WO 2006/071740, which is incorporated herein by reference in its entirety.
Various salts, crystalline forms, formulations, and uses of (R)-8-chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine, have been reported in U.S. provisional applications 61/402,578, 61/403,143, 61,402,580, 61/402,628, 61/403,149, 61,402,589, 61/402,611, 61/402,565, and 61/403,18, each of which is incorporated herein by reference in its entirety.
(R)-8-Chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride (lorcaserin hydrochloride) is an agonist of the 5-HT2C receptor and shows effectiveness at reducing obesity in animal models and humans. In December 2009, Arena Pharmaceuticals, Inc. submitted a New Drug Application, or NDA, for lorcaserin to the FDA. The NDA submission is based on an extensive data package from lorcaserin's clinical development program that includes 18 clinical trials totaling 8,576 patients. The pivotal phase 3 clinical trial program evaluated nearly 7,200 patients treated for up to two years, and showed that lorcaserin consistently produced significant weight loss with excellent tolerability. About two-thirds of patients achieved at least 5% weight loss and over one-third achieved at least 10% weight loss. On average, patients lost 17 to 18 pounds or about 8% of their weight. Secondary endpoints, including body composition, lipids, cardiovascular risk factors and glycemic parameters improved compared to placebo. In addition, heart rate and blood pressure went down. Lorcaserin did not increase the risk of cardiac valvulopathy. Lorcaserin improved quality of life, and there was no signal for depression or suicidal ideation. The only adverse event that exceeded the placebo rate by 5% was generally mild or moderate, transient headache. Based on a normal BMI of 25, patients in the first phase 3 trial lost about one-third of their excess body weight. The average weight loss was 35 pounds or 16% of body weight for the top quartile of patients in the second phase 3 trial.
In view of the growing demand for compounds useful in the treatment of disorders related to the 5-HT2C receptor, (R)-8-chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine has emerged as an important new compound. Accordingly, new processes and intermediates for the production of (R)-8-chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine salts are needed. The processes and intermediates described herein help meet these and other needs.